1. Field of the Invention
One embodiment of the present invention relates to a light-emitting element.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a storage device, a method for driving any of them, and a method for manufacturing any of them.
2. Description of the Related Art
Light-emitting elements utilizing electroluminescence have been currently under active research and development. In a basic structure of the light-emitting element utilizing electroluminescence, a layer containing a light-emitting substance (hereinafter, the layer is referred to as a “light-emitting layer”) is interposed between a pair of electrodes. By voltage application between the pair of electrodes of the light-emitting element, light can be emitted from the light-emitting substance.
In the manufacturing process of a light-emitting element, an electrode serving as an anode of the light-emitting element is formed over a substrate before the other electrode serving as a cathode is formed as described above in some cases, and in other cases, an electrode serving as a cathode is formed over a substrate before the other electrode serving as an anode is formed. An element structure formed in the former cases of the manufacturing process is referred to as an “ordered structure”, and an element structure formed in the latter cases is referred to as an “inverted structure”. Not only these element structures of the light-emitting element are mutually inverted over a substrate, but also the element structures may differ from each other depending on the difference in manufacturing processes (e.g., Patent Document 1).
Furthermore, a structure in which an oxide semiconductor (OS) is used for a semiconductor layer of a field effect transistor (FET) for controlling a light-emitting element has also been proposed. In particular, since an OS-FET using indium gallium zinc oxide (IGZO) as an oxide semiconductor is an n-type transistor in which the majority carriers are electrons, a combination of the OS-FET and the inverted-structure light-emitting element whose electrode connected to the OS-FET serves as a cathode has been proposed as the way to improve element characteristics (e.g., Non-Patent Document 1).